Beauty Quicksort

void quicksort(int l, int u) {
    int i, m;
    if (l >= u) return;
    m = l;
    for (i = l+1; i <= u; i++)
        if (x[i] < x[l])
            swap(++m, i);
    swap(l, m);
    quicksort(l, m-1);
    quicksort(m+1, u);
}


// https://www.youtube.com/watch?v=QvgYAQzg1z8